I have dual booted Linux/Grub and OpenBSD reliably for several years.
In my setup, on a single HD, Linux and OpenBSD share the same ESP
partition with BOOTX64.EFI copied over to the ESP. I pre-format a
partition for OpenBSD, typically from Linux or Gparted. This setup
updates without issue and also deals with the sha256 checksum.
I documented it here:
https://daemonforums.org/showthread.php?t=9894
I'm planning on taking another shot at shimming from Grub to OpenBSD on
the M2 nvme drive when 7.9 is released. FreeCAD 1.1 just made it under
the wire for new ports and it worth the time trying to run OpenBSD from
the M2_1 slot. The difference in processing speed on linux, both with
firefox-esr and FreeCAD is obvious.
This grub entry boots devuan from the M2_1 slot:
insmod part_gpt
insmod ext2
search --no-floppy --fs-uuid --set=root ba4e6496-4f9a-41a4-bb60-c78b4b59ac13
My lsblk -f output:
nvme0n1
├─nvme0n1p1 vfat FAT32 95C8-F0BC 965.3M 1% /boot
├─nvme0n1p2 ext4 1.0 ba4e6496-4f9a-41a4-bb60-c78b4b59ac13 44G
14% /
├─nvme0n1p3 swap 1 b592f6d7-8b02-48ce-8a80-30820032127e
[SWAP
└─nvme0n1p4 ext4 1.0 855d22c0-df08-4fde-a614-944b1960917f 780.1G
1% /home
There is a grub module for ufs
I plan to modify /etc/grub.d/40_custom to
insmod part_gpt
insmod ufs
search --no-floppy --fs-uuid --set=root "uuid for openbsd /"
chainloader EFI/BOOT/BOOTX64.EFI
I previously was using the uuid for the FAT32 partition but it is
actually /. You can pull the nvme0n OpenBSD uuid's from the linux
install.
Beyond working as a shim to M2 drives, Grub would also be useful for
those who want to run release and current OpenBSD on a single machine.
Grub_v1 used to be in ports and FreeBSD/NetBSD offer Grub2.
Additionally, Grub can be installed standalone and on Windows. I think
it's a viable option and should not affect upgrades/checksumming.
Lloyd wrote:
GRUB is a Rube Goldberg machine. I would not use it to boot OpenBSD.
I suspect it could keep bsd.rd or sysupgrade from working properly.
I have a similar issue with a Linux machine. The fix is to locate *both*
the bootloader and kernel on a device the BIOS (and bootloader) can read
before the kernel is fully initialized. Put everything else on the SSD.
In Linux this would be /boot. Under OpenBSD, this means /.
Fortunately / can be very small on OpenBSD. 512MB is more than enough.
Regards
Lloyd
On Apr 17, 2026: 19:52, Jan Stary wrote:
On Apr 17 08:50:17, [email protected] wrote:
I use my OpenBSD workstation for CAD drafting and the parametric
generation of CAD files should be speed up by running the faster drive.
On an MSI b840m-b board with a WD 7100 m2_2280 drive, OpenBSD installs
to the drive (sd0 option) without issue. On the other hand, MSI's bios
does not recognize the M2_1 drive as a boot option.
If the thing that is slow is writing the actual CAD files,
have /home (or /cad or wherever you do it) on the fast nvme,
having the system installed and booting from another disk
that your BIOS recognizes as bootable.
--
J. Scott Heppler
